The metronome has one job:
beep or vibrate reliably at a configurable interval.
I do not really care if it is exactly 170bpm or whatever i configure, but it seems the cpu of my 750€ watch is busy doing something that prevents it beeping at the correct time.
it basically beeps randomly just making sure it beeped 170 times per minute, not every time 1/170 of a minute.